Diplomacy is a popular seven-player zero-sum board game that involves simultaneous moves and both cooperation and competition. Players decide whom to support and whom to betray in pursuit of majority control of the board. Diplomacy has a long history as a benchmark for AI research [1]}, [2]}, [3]}, [4]}, [5]} and has been a particularly active domain for research in recent years [6]}, [7]}, [8]}. Since the game state is fully observable each turn, and players act simultaneously, each turn in Diplomacy can be viewed as a normal-form game if there is a defined state value function. Moreover, since players are able to communicate before acting, it is possible for players' actions to be correlated.
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